1. Field of the Invention
The present invention relates to a hard disk drive and a method of controlling a flying height of a magnetic head of the hard disk drive, and more particularly, to a hard disk drive for measuring a flying height of the magnetic head using a preamble signal of the servo pattern in real time and controlling the flying height of the magnetic head to a target flying height based on this and a method of controlling a flying height of a magnetic head of the hard disk drive.
2. Description of the Related Art
Hard disk drive, which is a storage device consisted of an electronic device and a mechanical device for converting digital electronic pulses into a more permanent magnetic field to record and reproduce data, is widely used as an auxiliary storage device of the computer system or the like in recent years since a large amount of data can be accessed at high speed.
The capacity of the hard disk drive has been increased by implementing high track per inch (TPI) and high bits per inch (BPI) in recent years. As the capacity of the hard disk drive is increased, the size of a write/read element of the magnetic head has been reduced, and thus the flying height (FH) of the magnetic head that flies on the disk surface has been gradually decreased.
In other words, when high track per inch (TPI) and high bits per inch (BPI) are implemented to fabricate a high-capacity hard disk drive, the width of a track is decreased, and if the width of a track is decreased, then the intensity of a magnetic field detected from the track is weakened. Accordingly, in this case, if the flying height (FH) of the magnetic head is increased, then it may cause difficulty in detecting a magnetic field, thereby further increasing the possibility that the operation of the hard disk drive is carried out in an inefficient manner.
Accordingly, studies on a method of properly controlling the flying height (FH) of a magnetic head to effectively reduce the flying height of the magnetic head with respect to the disk have been actively carried out, and flying on demand (FOD) is taken into consideration for one of them.
Flying on demand (FOD) is a method of controlling the flying height of a magnetic head using a magnetic head flying height reduction characteristic being occurred when a pole tip that is an end portion of the magnetic head is thermally expanded while the hard disk drive is operated by applying a constant voltage (FOD voltage) to a heater which is built in the magnetic head.
However, the environments in which the hard disk drive is used in actuality are quite varied and thus the flying height of a magnetic head cannot always have the sameness, and thus even if a FOD voltage required for the target flying height is applied to a user environment in which the hard disk drive is used, the flying height of the magnetic head may be varied according to the user's environment.
In particular, the flying height of the hard disk drive may be mostly affected by a change of the ambient temperature and atmospheric pressure, and thus when the hard disk drive is used in a user's environment by applying a unified reference FOD voltage profile it may occur a case where the target flying height of the magnetic head cannot be maintained by a complicated operation due to various environmental parameters, and therefore, when the target flying height of the magnetic head cannot be maintained as described above, there is a drawback of causing weak write or head/disk interference (HDI) related problems.